Fig. (1) Optimization of the GLA assay. (a) GLA activity at different pH values. The optimal pH was 5.9. (b) Effect of sodium taurocholate. GLA activity decreased with increasing concentrations of sodium taurocholate. (c) Enzyme concentration-response. The enzyme activity increased nearly linearly from 0.125 to 4 nM GLA. (d) DMSO tolerance. Fluorescence slightly decreased as DMSO concentration increased.